This invention relates to a process for the preparation of nitro-substituted diphenyl ethers from aromatic nitro compounds. The nitro-substituted diphenyl ethers are useful intermediates for the synthesis of amino-substituted diphenyl ethers which are useful as intermediates for the synthesis of various commercial products, including polymers, dyes, and plasticizers. For example, they may be readily reduced to form diamines which are useful in the preparation of polyimide resins.
R. L. Markezich and O. S. Zamek disclose (J. Org. Chem. vol. 42, 3431, (1977)) that heating a solution of 4-nitro-N-methylphthalimide with potassium fluoride, potassium nitrite, or sodium nitrite, in solvents such as DMF, dimethyl sulfoxide, or N-methyl pyrrolidone at temperatures of 142.degree.-190.degree. C. produced 4,4'-oxybis(N-methylphthalimide) in yields up to 78%. The authors also disclose that neither potassium fluoride nor potassium nitrite were effective in producing the corresponding diphenyl ether from 4-nitrophthalic anhydride (J. Org. Chem. Vol. 42, 3435 (1977)).
German Patent 2,037,781 (as abstracted in Derwent accession number 72-10017t/07) discloses that para-nitro-benzonitrile forms 4,4'-oxybis(benzonitrile) when reacted with sodium nitrite in a polar organic solvent at a temperature of 100.degree.-220.degree. C.
Japanese patent 80 24125 (as abstracted in Chem. Abstracts 93:167885z) discloses that 1,4-dinitrobenzene may be treated with alkali metal salts or alkali metal hydroxides in polar organic solvents to produce 4,4'-dinitrodiphenyl ether. A similar reaction occurs with 1-cyano-4-nitrobenzene to form 4,4'-dicyanodiphenyl ether.
Japanese patent 78 90230 (as abstracted in Chem. Abstracts 90:22570w) discloses that para-substituted nitro-benzenes react with alkali or alkaline earth metal nitrites in the presence of phase transfer catalysts to form para-substituted diphenyl ethers. The para substituents disclosed are nitro and cyano. In addition, a similar reaction is reported for 1,2-dinitro-4-methylbenzene. In this case, it is the nitro group para to the methyl substituent which is displaced, and not the meta-nitro group and, accordingly, the product is 2,2'-dinitro-4,4'-dimethyl diphenyl ether.
U.S. Pat. No. 4,558,164 discloses a process for the converting ortho or para-nitrochlorobenezene or ortho or para-nitrofluorobenezene into symmetrical dinitrophenyl ethers in a polar organic solvent using a salt of a carboxylic acid, such as benzoic acid or acetic acid as a catalyst and potassium or sodium carbonate as reagents. In the reaction, the halogen atoms of two molecules of the starting material are displaced by oxygen to form the diphenyl ether. The nitro groups are not involved in the condensation.
U.S. Pat. No. 4,933,469 discloses a method for preparing oxybisphthalimides by heating a nitro phthalimide compound in the presence of an alkali metal carboxylate and a phase transfer catalyst in a nonpolar organic solvent. The alkaline metal carboxylate is present in the range from about 0.1 to about 5 moles per mole of nitrophthalimide (10-500 mole percent) and the phase transfer catalyst can be utilized within the range of 2.5 to 30 mole percent. The phase transfer catalyst disclosed are diorganoaminopyridinium salts.
U.S. patent application Ser. No. 594,479, co-pending herewith, discloses that 3,5-dinitrobenzotrifluoride may be reacted, "in an organic solvent in the presence of water and about two equivalents (based on the product weight) of potassium or cesium fluoride" to form 1,1'-oxybis(3-trifluoromethyl-5-nitrobenzene).